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1500 questions
44
votes
4 answers
What is the minimum pressure of a medium for which a sound wave can exist?
At what pressure will be particles in a medium be unable to form a sound wave when disturbed? How can this pressure be described mathematically?
My guess is that this would correspond to the point at which the restoring force due to pressure is…
uqtredd1
- 555
44
votes
5 answers
Where does deleted information go?
I've heard that, in classical and quantum mechanics, the law of conservation of information holds.
I always wonder where my deleted files and folders have gone on my computer. It must be somewhere I think. Can anyone in principle recover it even if…
an offer can't refuse
- 6,035
44
votes
2 answers
Wick rotation in field theory - rigorous justification?
What is the rigorous justification of Wick rotation in QFT? I'm aware that it is very useful when calculating loop integrals and one can very easily justify it there. However, I haven't seen a convincing proof that it can be done at the level of…
user17116
44
votes
4 answers
How does one detect a single photon?
I understand the double slit experiment up until the point that we begin "detecting" single photons. What does it mean to detect. You cant place a camera in the slit because that would capture the photon just like the photosensitive plates…
SlightlyCyborg
- 611
44
votes
6 answers
Pouring water in an aircraft while upside down?
What is the physics behind the following photo?
Someone had told me that this is because the aircraft might be moving towards a lower altitude, but I am still not sure.
Sufiyan Ghori
- 731
43
votes
7 answers
Why are Only Real Things Measurable?
Why can't we measure imaginary numbers? I mean, we can take the projection of a complex wave to be the "viewable" part, so why are imaginary numbers given this immeasurable descriptor? Namely with operators in quantum mechanics, why must measurable…
user24082
43
votes
5 answers
How can any light get past a polarizer?
The sun sends out unpolarized light. There are infinite degrees in which these photons are oriented. A polarizer only lets in light of one specific orientation.
In statistics, the infinitesimal area/slice of a single value in a continuous…
kevinbuiied
- 559
43
votes
3 answers
What is the smell after quartz is rubbed together?
When I rub quartz together, it glows due to triboluminescence but it also creates a burnt smell. What causes that smell?
The Seal
- 403
43
votes
10 answers
When a cork is pulled out of a wine bottle, why does the inner end often expand more than the outer end?
When I pull a cork out of a wine bottle, it usually expands slightly in circumference. This makes sense: you want the cork to be slightly compressed relative to its natural diameter when it's inside the bottle in order to make a tight seal.
But I've…
tparker
- 47,418
43
votes
10 answers
Why can atoms only gain or lose electrons and not protons?
I know that an object can become net negative or net positive by losing or gaining electrons, and having more or fewer protons than electrons but why can't protons be transferred too?
user17886134
- 595
43
votes
4 answers
Will a penny ever stand still in the water at a certain depth?
Let’s say I drop a penny in the deepest part of the ocean having a certain depth. Would the penny become buoyant enough to stand still in the water, since the density of water increases with depth? Since the buoyancy of objects becomes greater as…
Justus Bozzi
- 419
43
votes
4 answers
Would we even notice the merger with the Andromeda Galaxy?
I have read this question:
When galaxies collide it is not that their stars crash into each other, because their individual cross-sections are extremely small when compared to the space between them. This is dealt with in qualitative terms on the…
Árpád Szendrei
- 28,452
43
votes
4 answers
Why do "relativistic effects" come into play, when dealing with superheavy atoms?
I have now read on the Wikipedia pages for unbihexium, unbinilium, and copernicium that these elements will not behave similarly to their forebears because of “relativistic effects”. When I read about rutherfordium, it too brings up the relativistic…
Curious Layman
- 1,666
43
votes
2 answers
Is our solar system really that odd?
I have been learning about the solar system from popular science shows. In these shows they suggest that, after having seeing around 2500 other solar systems, astronomers have concluded that our solar system is not the normal one. They see sun…
Ben Sprott
- 1,420
43
votes
5 answers
If the gravitational force were inversely proportional to distance (rather than distance squared), will celestial bodies fall into each other?
If gravity was inversely proportional to distance, will the dynamics of celestial bodies be much different from our world? Will celestial bodies fall into each other?
Argyll
- 589